This invention relates to surgical retractors, and more particularly pertains to a new and improved surgical retractor of the dilating type.
In commencing a surgical procedure, a general surgeon makes one or more incisions in a human body. In order to obtain unhindered access to underlying anatomical features, the surgeon then uses a retractor to dilate or reflect the skin or underlying layers of tissue. A typical retractor is formed from surgical steel and includes one or more smooth projections, called blades, which are mounted normal to the handle and retain an area of tissue adjacent to an incision. (The term "blade" is thus a term of art as used herein, because no sharp edge is required.) A simple retractor may include only a blade attached to a handle. If a blade is curved, it may be described as being a certain number of inches or millimeters deep and a certain number of inches or millimeters spread. The surface of a blade may be described as being either closed-end (solid) or open-end (open within the periphery). A finger-like blade may have either a blunt or pointed tip.
A conventional hand-held self-retaining dilating retractor features a pair of levers which are fulcrumed to each other between their ends. Each lever includes a rear end constituting a handle and a front end to which one or more blades are mounted. The pivot lies between each lever's front end and its rear end. As the handles are closed, the front ends spread apart, causing the blades to recede from each other. One handle carries a curved rachet and a thumb-operated pawl is pivotally mounted to the other handle.
One advantage of using such a retractor is that the user may use one hand to operate the retractor, freeing the other hand to perform other functions such as inserting sponges and the like. This convenience may allow a procedure to be performed using a smaller surgical staff, thereby reducing labor costs.
In the modem medical practice, a surgeon may perform the same type of procedure many times per day. Members of the surgical staff who would use a hand-held dilating retractor during procedures in which the length of the incision is relatively great and the forces exerted by the tissue upon the retractor are relatively large might suffer from fatigue and be subject to injury resulting from the necessity repeatedly to supply pressure to close the handles against a relatively high resistance of tissue until the pawl and rachet are engaged. A surgeon must consider these factors when deciding whether a hand-held dilating retractor is practical for use in certain procedures.
For these reasons, it is important that the retractor efficiently transmit force exerted by the user's hand to the blades. Limitations on conventional hand-held dilating retractors lead many surgeons to reject their use during certain procedures.
U.S. Pat. No. 1,018,868 disclosed a hand-held dilating speculum and retractor which included a pair of main levers each having a main blade and a pair of supplemental levers each having a supplemental blade. The pair of main levers were between the pair of supplemental levers, such that a side of each supplemental lever contacted a side of its adjacent main lever. The main levers were fulcrumed to each other by a countersunk rivet constituting a main pivot, so that as the handles of the main levers were moved toward each other (closed), the main blades receded from each other (opened). Each supplemental lever was fulcrumed to its adjacent main lever by a shouldered screw 3 extending through a longitudinally extending straight slot 4 in the supplemental lever and threaded in such main lever. Shouldered screws 3 were positioned slightly to the rearward of the main pivot. A pin 6 mounted to each main lever handle extended through a longitudinally extending straight longitudinal slot 5 in the handle of its adjacent supplemental lever. Thus, closing the handles of the main levers transmitted force through pins 6 to the handles of the supplemental levers, opening the pair of supplemental blades along with the pair of main blades. The facing surfaces of the supplemental lever handles were convexly curved, and a pin 8 mounted to each main lever handle projected a sufficient distance to extend alongside this convex surface of its adjacent supplemental lever handle. Closing the pair of main lever handles caused pins 8 to slide along the convex surfaces of the supplemental handles, thus causing the supplemental levers to move rearwardly with respect to the pair of main levers, such rearward motion guided by sliding of screws 3 in slots 4 and pins 6 in slots 5.
The device as above described was mechanically inefficient; the closing of the pair of main lever handles exerts transverse force to pins 8, which works well to open the blades but must be redirected to exert longitudinal force through the constraint of the convex surfaces. As much of the force exerted by pins 8 on the convex surfaces is normal to rather than parallel to the convex surfaces, friction is thereby generated between pins 8 and the convex surfaces. Friction also is generated by forces exerted by screws 3 normal to the surfaces forming slots 4. Thus, in order to obtain free movement of the device, it was necessary to employ a lubricant. The lubricant was difficult to keep sterile, and as the operative area was close to the lubricated surfaces, particularly those located on the supplemental lever handle facing the patient, there was danger of infection from this source. The inventor himself later described this device as being more or less impractical.
A subsequent device by the same inventor, disclosed in U.S. Pat. No. 1,500,227, enlarged the main lever handles and provided convexly curved slots therein, described as being cam slots, receiving pins extending from the respective adjacent supplemental lever handles. While this later device provided the convex surfaces at a location more to the rearward from the operative area to reduce the danger of infection, it remained more or less the same in terms of its mechanical inefficiency.